(1) Field of the Invention
The present invention relates to electromagnetic clutches used for transmitting rotation from one, for example, a pulley rotated by an automative engine, to another, for example, a drive shaft of an automative air conditioning compressor.
(2) Description of the Prior Art
Such an electromagnetic clutch comprises an armature plate mounted on a first rotatable member, a second rotatable member having an electromagnetic friction surface and rotatably supported by a bearing on a mount, and an electromagnetic device mounted by a supporting plate on the mount for generating a magnetic force to attract the armature plate to the electromagnetic friction surface to enable transmission of rotation between the first and the second rotatable members, as is disclosed in, for example, U.S. Pat. No. 4,227,600 (Reference 1) issued to SHIRAI, and assigned to SANKYO ELECTRIC COMPANY, LIMITED, GB-A-2156013 (Reference 2) by SANDEN CORPORATION, and others.
In such electromagnetic clutches, the electromagnetic device and the bearing are required to be firmly supported on the mount without unintended vibration during rotation of the pulley for reliable operation of the clutch and without any axial movement of the electromagnetic device and the second rotatable member even when the electromagnetic device is energized. Further, it is required that the second rotatable member and the electromagnetic device are readily and simply mounted on the mount for assembling the clutch.